The invention relates to a magnetic final control element for a regulator apparatus particularly for use in an electronically regulated fuel injection system for motor vehiches.
In a magnetic final control element of this type, experimentally tested in connection with Diesel fuel injection systems for motor vehicles, the restoring spring is embodied as a helical compression spring which concentrically surrounds the displacement transducer and disposed adjacent to the magnet in the final control element assembly housing, with a course of its longitudinal axis arranged parallel to the central axis of the magnet, along which the armature moves. The force-displacement coupling between the armature of the magnet and the restoring spring is provided by a pivot lever articulated on the rear wall of the housing which actuates the final control element. One end of the restoring spring and the armature of the electromagnet both contact the free end of one arm of the pivot lever.
The restoring spring is supported between the bottom of the housing, on which the exciter coil of the magnet with its core is also affixed, and a support part which is displaceably guided in its axial direction. Also, this support part is connected with the transducer rod of the inductive transducer, which projects into the takeup spool which is also affixed to the floor of the housing.
A magnetic final control element of the type described above has material disadvantages.
The disposition of the magnet and the restoring spring which surrounds the displacement transducer requires a great deal of installation space, and the final control element housing is accordingly voluminous. Since the control force of the electromagnet and the restoring force of the restoring spring are each in contact with the large arm of the pivot lever, working in opposite directions like a force pair, and thus tend with accordingly increased force to tip the pivot axis of the pivot lever, then first the housing part which supports the pivot bearing must be very stable in its embodiment (generally it is a cast metal piece) and second the pivot lever must also be embodied as sufficiently bend- and torsion-resistant, so that errors of the armature stroke are, as much as possible, not transmitted to the displacement transducer. However, such errors of transmission which result from the play in the bearing of the pivot lever and/or from changes in friction ratios due to wear in the region of the connection with the armature and with the restoring spring are unavoidable.